The aircraft was operating normally prior to impact and is not considered to be a factor in the accident. Also, there was no pre-existing physiological condition found that might have impaired the pilot's performance. Radar data showed that the aircraft was flown along terrain contours at altitudes well below that required for effective observation. The aircraft was flown consistently below 500feet agl, and recorded on radar as low as 150to 250feetagl. When the aircraft struck the tree, it would have been only 55to 60feet above the ground. The aircraft was in a wings-level attitude when it struck the tree. This tree was sticking up above the others, but may have blended in with trees in the background. This could explain why the pilot did not see the tree and take evasive action to avoid it, or his attention may have been focussed on observing the pipeline to his left. The following Engineering Branch report was completed: LP 012/02 - Instrument ExaminationAnalysis The aircraft was operating normally prior to impact and is not considered to be a factor in the accident. Also, there was no pre-existing physiological condition found that might have impaired the pilot's performance. Radar data showed that the aircraft was flown along terrain contours at altitudes well below that required for effective observation. The aircraft was flown consistently below 500feet agl, and recorded on radar as low as 150to 250feetagl. When the aircraft struck the tree, it would have been only 55to 60feet above the ground. The aircraft was in a wings-level attitude when it struck the tree. This tree was sticking up above the others, but may have blended in with trees in the background. This could explain why the pilot did not see the tree and take evasive action to avoid it, or his attention may have been focussed on observing the pipeline to his left. The following Engineering Branch report was completed: LP 012/02 - Instrument Examination On this flight, the pilot consistently flew the aircraft below the required altitude for effective observation and inadvertently struck a tree.Findings as to Causes and Contributing Factors On this flight, the pilot consistently flew the aircraft below the required altitude for effective observation and inadvertently struck a tree.